Is the birthday of Prophet Muhammad s.a.w.s. on 12th of Rabbi-Awwal? How did they come up with this precise date in an era when there were no calendars, etc.? When did the Prophet s.a.w.s. pass away?

Historians differ as to the birthday of Rasulullah (Sallallaahu Alayhi%0D%0AWasallam). Many have preferred the view of it being 12 Rabi-ul-Awwal.%0D%0ARasulullah (Sallallaahu Alayhi Wasallam) passed away on 12 Rabi-ul-Awwal.%0D%0AThis has been recorded in authentic narrations.%0D%0A%0D%0ADetermination of dates is not dependent on printed calendars. The Islamic%0D%0Acalendar is lunar. Thus, by the sighting of the moon all the people know%0D%0Athat it is the first of the month, and based on this can determine which is%0D%0Athe 12 of the lunar month.%0D%0A%0D%0Aand Allah Ta'ala Knows Best%0D%0A%0D%0AMoulana Imraan Vawda%0D%0AFATWA DEPT.%0D%0A%0D%0ACHECKED AND APPROVED CORRECT: Mufti Ebrahim Desai%0D%0A%0D%0AQ: What is the correct view on the date of Rasulullah's (Sallallaahu Alayhi%0D%0AWasallam) birth and demise?%0D%0AA: According to the majority opinion, Rasulullah (Sallallaahu Alayhi%0D%0AWasallam) was born in the month of Rabi-ul-Awwal, in the year of the%0D%0Aelephant. The day of his birth was Monday.%0D%0A%0D%0AHadhrat Abu Qataadah (Radhiallaahu Anhu) narrates that Rasulullah%0D%0A(Sallallaahu Alayhi Wasallam) was asked regarding the fast of Monday. He%0D%0Areplied, 'It is the day I was born and also the day when the first%0D%0Arevelation was sent upon me.' (Muslim vol1 pg.368; Deoband).%0D%0A%0D%0AThere are differences of opinion on the date of Rasulullah's (Sallallaahu%0D%0AAlayhi Wasallam) birth. Allaamah Kawthari (RA) prefers the 9th of%0D%0ARabi-ul-Awwal. (Maqaalaatul Kawthari pg.405 - 207). Allaamah Qastalaani (RA)%0D%0Astates that the majority of the Muhadditheen and historians have also%0D%0Apreferred the 9th of Rabi-ul-Awwal.%0D%0A%0D%0ARasulullah (Sallallaahu Alayhi Wasallam) passed away in Rabiul-Awwal on a%0D%0AMonday. As regards the date of his demise, there are three opinions: 1, 2%0D%0Aand 12 Rabi-ul-Awwal (Bidaaya Wan Nihaaya vol.5 pg.275)%0D%0A%0D%0AThe 9th Dhul-Hijjah (day of Arafah) in the year 10AH (the year which%0D%0ARasulullah (Sallallaahu Alayhi Wasallam) performed Hajj) was a Friday. If%0D%0Athe months Dhul-Hijjah, Muharram and Safar, all were 30 days, or 29 days or%0D%0Asome 29 and others 30 days, the 12th Rabi-ul-Awwal did not fall on a Monday.%0D%0ATherefore, the preferred view of the date of Rasulullah's demise is the 1st%0D%0Aor 2nd Rabi-ul-Awwal. Ibn Jarir (RA) prefers the 1st Rabi-ul-Awwal while Ibn%0D%0AHajar prefers the 2nd Rabi-ul-Awwal. (Al-Mawaahib with Zarqaani vol.1%0D%0Apg.131) - Al-Mahmood 15